LED Flashing Application

RationalRand · Feb 1, 2012

Hello,

I was wondering if having a standard 120volt led lamp flash on for 2 - seconds and off for 4 - seconds continuously will lower the lifespan of the bulb. Sylvania has an 8-watt A-Line series lamp that I would like to use in a fixture that will flash continuously 24/7/365.

Also, the fixture is totally enclosed so there is no venting for heat issues.

Thank you so much.

RR

RoGuE_StreaK · Feb 1, 2012

If anything, I should imagine it will increase it's lifespan, as it's off for 2/3 of the time. So theoretically it should last you three times longer than if it was permanently on 24/7
Also, this off period should help greatly reduce any heat issues. Of course, if it's badly designed nothing can help there. But I've always associated Osram with good products, so should be well designed (no concrete proof though)

Though are you saying that the fixture you are putting it in is completely sealed? If so, that would be the major area of focus for me, no matter how well designed the bulb is, if it can't take advantage of any of it's clever heatsink design then it may well fail. Run it permanently on for quite some time and see how the heat goes.

Flashing isn't your issue here for lifespan, build-up of heat from bad heatsinking may be the killer. Doesn't necessarily need venting, but most likely will need some sort of thermal path to get heat from the LED body to the outside world.

RationalRand · Feb 1, 2012

RoGuE_StreaK said:
If anything, I should imagine it will increase it's lifespan, as it's off for 2/3 of the time. So theoretically it should last you three times longer than if it was permanently on 24/7
Also, this off period should help greatly reduce any heat issues. Of course, if it's badly designed nothing can help there. But I've always associated Osram with good products, so should be well designed (no concrete proof though)

Though are you saying that the fixture you are putting it in is completely sealed? If so, that would be the major area of focus for me, no matter how well designed the bulb is, if it can't take advantage of any of it's clever heatsink design then it may well fail. Run it permanently on for quite some time and see how the heat goes.

Flashing isn't your issue here for lifespan, build-up of heat from bad heatsinking may be the killer. Doesn't necessarily need venting, but most likely will need some sort of thermal path to get heat from the LED body to the outside world.

Thank you for helping me with this problem. I truly appreciate it. I have been looking for this answer for a few hours now.

Do you mind if I give you a little bit more info about the fixture in order to address the heating issue? The fixture is a red, yellow, green type traffic signal fixture. It's rather large 36" X 12" and each lamp socket has a silver reflector behind it in order to reflect the light straight out of the fixture. The lamps will be mounted horizontally. Unfortunately there is no venting because the fixture used to be outside and now it is inside.

Do you still believe that I am going to have some performance issues? If so, can you recommend a way to get the heat to the outside world?

Best To You!

RR

qwertyydude · Feb 1, 2012

Best way to get the heat to the outside world is use a good chunk of aluminum that can stick out the back and be exposed to air. It will mean having to remove the socket assembly entirely so you have room to make an led fixture that can fit through the hole but have the heat sink sticking out the back.

RationalRand · Feb 1, 2012

qwertyydude said:
Best way to get the heat to the outside world is use a good chunk of aluminum that can stick out the back and be exposed to air. It will mean having to remove the socket assembly entirely so you have room to make an led fixture that can fit through the hole but have the heat sink sticking out the back.

I can almost picture that just like you said it. There is a problem that I should have mentioned in the previous post and that is, I cannot modify the fixture. I was hoping to run a piece of sheet metal from the heat sink to the outside through the door in the traffic signal.

RoGuE_StreaK · Feb 1, 2012

If it's going to be inside out of the weather, then couldn't you say drill some holes for ventilation and maybe fit a PC case fan? Or completely chop out two sections, eg. top and bottom, and install case fans with grills (eg like any number of these), one blowing, one sucking, should then look stock?

RationalRand · Feb 2, 2012

RoGuE_StreaK said:
If it's going to be inside out of the weather, then couldn't you say drill some holes for ventilation and maybe fit a PC case fan? Or completely chop out two sections, eg. top and bottom, and install case fans with grills (eg like any number of these), one blowing, one sucking, should then look stock?

I am unable to modify the fixture.

How do the LED traffic signals deal with heat?

Thanks for all of the great ideas.

AnAppleSnail · Feb 2, 2012

RationalRand said:
I am unable to modify the fixture.

How do the LED traffic signals deal with heat?

Thanks for all of the great ideas.

Having taken apart LED traffic light units, I can tell you. LED traffic lights press the LED heatsink against the metal outsides of the case, but some have poorly made heatsinks.

The ones I took apart had:
LED board connected to the aluminum fins that sit in an octagonal plastic/metal dome
This metal/plastic dome is a faceted shape. Plastic layers on each side of metal, about 0.5mm thick - reasonably conductive, electrically insulative though. They only work due to LARGE contact area (about the size of a piece of paper)
This dome is pressed against the yellow housing.

RationalRand · Feb 2, 2012

AnAppleSnail said:
Having taken apart LED traffic light units, I can tell you. LED traffic lights press the LED heatsink against the metal outsides of the case, but some have poorly made heatsinks.

The ones I took apart had:
LED board connected to the aluminum fins that sit in an octagonal plastic/metal dome
This metal/plastic dome is a faceted shape. Plastic layers on each side of metal, about 0.5mm thick - reasonably conductive, electrically insulative though. They only work due to LARGE contact area (about the size of a piece of paper)
This dome is pressed against the yellow housing.

Hello AnAppleSnail,

I like your name. May I inquire what the meaning is?

Thanks for the advice on my application. I am thinking about using the SYLVANIA A-LINE 8 or 12 or 13 WATT LAMP. If I were to slide a big fat metal washer onto the lamp heat sink and screw the lamp into the socket so that the fat washer is pressed up against the reflector would this carry the heat away from the lamp effectively?

Thank You and All The Best To You !!!

RR

AnAppleSnail · Feb 2, 2012

RationalRand said:
Hello AnAppleSnail,

I like your name. May I inquire what the meaning is?

Thanks for the advice on my application. I am thinking about using the SYLVANIA A-LINE 8 or 12 or 13 WATT LAMP. If I were to slide a big fat metal washer onto the lamp heat sink and screw the lamp into the socket so that the fat washer is pressed up against the reflector would this carry the heat away from the lamp effectively?

Thank You and All The Best To You !!!

RR

In high school and college I kept an aquarium on my desk. The snails grew very large, up to golf-ball size. They also did interesting things like eat my fish, so I kept the name.

It really depends on what the reflector is made of. The traffic lights press flat surfaces against each other, creating a respectable contact area. For low-heat-transfer materials like plastic, a large contact area is needed to move moderate heat. Is the reflector substantial metal? If so, it will provide a few watts of cooling. If not, then I suggest putting sheet metal inside the housing so that it slurps heat from the LED to the walls of the housing.

A few pictures (Perhaps using the 'Macro' setting on your camera) will be worth a dozen posts describing the housing.

LED Flashing Application

RationalRand

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RoGuE_StreaK

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RationalRand

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qwertyydude

Flashlight Enthusiast

RationalRand

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RoGuE_StreaK

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RationalRand

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AnAppleSnail

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RationalRand

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AnAppleSnail

Flashlight Enthusiast

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